Systems and methods for neuromodulation using pre-recorded waveforms

ABSTRACT

Methods for neuromodulation using waveform signals. In certain embodiments, an input waveform is obtained from a signal source site in a source subject and an output waveform is applied to a target site in a target subject. The source subject is a human or animal and the signal source site is in the nervous system, including the brain. The source subject and target subject are the same subjects or different subjects. The output waveform is identical to the input waveform or derived from the input waveform. In some embodiments, the output waveform is modified in response to physiologic feedback. Also provided are systems for neuromodulation using waveform signals.

RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 11/522,029 entitled “SYSTEM AND METHOD FOR PROVIDING A WAVEFORMFOR STIMULATING BIOLOGICAL TISSUE” filed on Sep. 15, 2006, now U.S. Pat.No. 7,715,912, which is a continuation-in-part of U.S. patentapplication Ser. No. 11/404,006, which was filed on Apr. 13, 2006, andentitled “SYSTEM AND METHOD FOR PROVIDING A WAVEFORM FOR STIMULATINGBIOLOGICAL TISSUE,” which claims the benefit of U.S. Provisional PatentApplication No. 60/671,011, which was filed Apr. 13, 2005, and entitled“SYSTEM AND METHOD FOR PROVIDING A WAVEFORM FOR STIMULATING BIOLOGICALTISSUE.” Each of the above-identified patent applications isincorporated herein by reference.

TECHNICAL FIELD

The present invention relates generally to neuromodulation usingelectrical stimulation.

BACKGROUND

Various types of stimulators have been developed for a variety ofin-vivo applications. For example, a stimulator can be employed forperforming spinal cord stimulation, deep-brain stimulation or forstimulation of other neurological paths, such as for treatment ofvarious disorders and diseases. Typically, each stimulator includes awaveform generator that generates its own waveform. For instance, a userdefines the necessary parameters and the stimulator constructs thewaveform accordingly. Usually the parameters include amplitude,frequency, phase symmetry and duty cycle. The more complex the waveform,the more parameters are necessary to describe the waveform. Implantablestimulators are constrained by space and typically cannot accommodatecomplex circuitry. Implantable stimulators, therefore, usually trade offwaveform complexity for saving space. Thus, there is a need foralternate designs for a stimulator capable of generating waveforms to beused in neuromodulation.

SUMMARY

In one aspect, the present invention provides a method forneuromodulation to treat paralysis or weakness due to a cortical injury,comprising: recording an input waveform from a first site in the nervoussystem in a first subject, wherein the first site is selected from thegroup consisting of: motor cortex, premotor cortex, thalamus, rednucleus, olivary nucleus, and dentate nucleus; and applying an outputwaveform to a second site in the nervous system in a second subject,wherein the second site is selected from the group consisting of: motorcortex, premotor cortex, thalamus, red nucleus, olivary nucleus, anddentate nucleus; wherein the output waveform is identical to the inputwaveform or derived from the input waveform.

In another aspect, the present invention provides a neurostimulationsystem comprising: memory that stores waveform data for at least onewaveform; a playback system that provides an output waveform based onthe waveform data in the memory; a sensor for sensing a bodily activity;and a controller in communication with the sensor, wherein, in responseto the bodily activity sensed, the controller controls the outputwaveform.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a block diagram of an embodiment of a programmablestimulation system that can be implemented according to an aspect of thepresent invention.

FIG. 2 depicts an example of yet another stimulation system that can beimplemented according to an aspect of the present invention.

FIG. 3 depicts a block diagram of an embodiment of an implantable pulsegenerator system that can be implemented according to an aspect of thepresent invention.

FIG. 4 depicts a block diagram of another embodiment of an implantablepulse generator system that can be implemented according to an aspect ofthe present invention.

FIG. 4A depicts a block diagram of one type of waveform controller thatcan be employed in the system of FIG. 4.

FIG. 4B depicts a block diagram of another type of waveform controllerthat can be employed in the system of FIG. 4.

FIG. 5 depicts an example of an implantable pulse generator device thatcan be implemented according to an aspect of the present invention.

DETAILED DESCRIPTION

The present invention provides systems and methods for neuromodulationusing waveform signals. As used herein, the term “waveform” describesthe amplitude versus time relationship for a signal and may encompassone or more periods of a given signal. The waveform can be a recordedsignal (which can be sampled and stored) or the waveform can begenerated by a waveform generating device (e.g., an oscillator or otherwaveform generator). For example, the waveform generator can constructor derive the waveform from a mathematical formula or based on a drawingor other visualization of a waveform that may be displayed on a screen.As used herein, the term “waveform” is also intended to includeneuro-electrical coding for communication (e.g., the sequence, timing,pattern, or frequency of neural firings). The waveform data in thememory can be preprogrammed, such as prior to implantation, or thewaveform data can be programmed post-implantation of the system.

In one aspect, the present invention provides methods of neuromodulationusing waveform signals. In certain embodiments, the method comprisesrecording an input waveform from a signal source site and applying anoutput waveform to a target site. In some instances, the input waveformsare obtained by recording an actual signal generated by a signal sourcesite in a human or animal body. The signal source site may be any partof the nervous system, including the central nervous system andperipheral nervous system (including the innervations at the endorgans).

These neural electrical signals may be known to control and/or regulatevarious body systems, including the nervous system, musculoskeletalsystem, endocrine system, immune system, pulmonary system,cardiovascular system, gastrointestinal system, or genitourinary system.As such, the recorded input waveforms may be associated with controllingand/or regulating certain bodily activity.

In some instances, the input waveform recordings are obtained from asite in the brain. Various parts of the brain may be the signal sourcesite, such as the brain stem, cerebral cortex, subcortical cerebralstructures, cerebellum including the deep cerebellar nuclei, basalganglia, dentate, thalamus, or any component of thedentato-thalamo-cortical pathway. In some cases, the recordings areobtained from the motor cortex, premotor cortex, thalamus, red nucleus,olivary nucleus, or dentate nucleus.

The input waveform recordings may be obtained from various human andnon-human source subjects. In some instances, the source subject is thesame as the target subject (i.e., the subject who is receiving theneurostimulation). In such cases, the recording may be obtained from aportion of the target subject's nervous system that is healthy or atleast partially functional. For example, where one part of the targetsubject's brain is diseased (e.g., due to a stroke), the recording maybe obtained from the corresponding contralateral brain structure that isnot affected by the disease. In other instances, the source subject andtarget subject are not the same. For example, the target subject may bea person, while the source subject may be another person or an animal,such as a non-human primate.

The input waveform recordings may be obtained from the source subject invarious settings. In some instances, the input waveforms are recordedfrom the source subject while undergoing surgery, such as brain surgery,spinal surgery, or peripheral nerve surgery. The source subject may beconscious, sedated, or under anesthesia during the surgery. In otherinstances, the input waveforms are recorded from the source subjectwhile at rest or while performing an activity or task. Such tasksinclude forelimb (upper extremity) tasks and hindlimb (lower extremity)tasks. For example, forelimb tasks include reaching, grabbing, pickingwith opposable thumbs, and grip squeezing; and hindlimb tasks includewalking. In some cases, a plurality of recordings are made to form alibrary of waveform recordings, with each recording associated with aspecific task, disease, or condition.

An output waveform is obtained based on the input waveform. The outputwaveform may be identical to the input waveform or a modification of theinput waveform. The input waveform may be modified in various ways toproduce the output waveform. For example, the input waveforms may bemodified to have a different pattern, intensity, amplitude, frequency,duration, pulse width, or number of pulse trains. In another example,additional pulses may be added to the input waveform. The additionalpulses may be added within the waveform or between waveforms. Theadditional pulses may be at pre-determined positions in the inputwaveform, at pre-determined intervals, or triggered by a spike in theinput waveform. In another example, the input waveforms may be modifiedby copying, cutting, pasting, deleting, cropping, appending, orinserting desired segments of waveforms. In another example, the outputwaveform may be a composite of a plurality of input waveforms, which canbe obtained from different signal source sites, different sourcesubjects, or different time points at the same signal source site.

The output waveform can be applied as neurostimulation to any of varioustarget sites in a target subject's body. The target site may be any partof the nervous system, including the central nervous system and theperipheral nervous system. In some instances, the target site is astructure in the brain. For example, the output waveform may be appliedto the brain stem, cerebral cortex, subcortical cerebral structures,cerebellum including the deep cerebellar nuclei, basal ganglia, dentate,thalamus, or any component of the dentato-thalamo-cortical pathway. Insome cases, the target site is the motor cortex, premotor cortex,thalamus, red nucleus, olivary nucleus, or dentate nucleus.

In some instances, the nervous system structure representing the targetsite anatomically corresponds to the nervous system structurerepresenting the signal source site. For example, the input waveformrecording can be obtained for one thalamus in one person and the outputwaveform can be applied to another thalamus in another person. In otherinstances, the nervous system structure representing the target site isdifferent from the nervous system structure representing the signalsource site. The target site may be neurologically proximal or distal tothe signal source site; or, where the source subject and target subjectare different, the target site may anatomically correspond to astructure that is neurologically distal to the signal source site. Forexample, an input waveform recording can be made in a thalamus and theoutput waveform can be applied to a cerebral cortex. In another example,an input waveform recording can be made in a cerebral cortex and theoutput waveform can be applied to a cerebellum. In another example, aninput waveform recording can be made in a cranial nerve nuclei and theoutput waveform can be applied to the cranial nerve itself.

The output waveform may be applied as neurostimulation using any ofvarious conventional means. In some cases, the stimulation is applied bydirect conduction. For example, the stimulation can be performed with anelectrode positioned at the target site. The electrode can be implantedpermanently, chronically, or temporarily. In other cases, thestimulation is applied externally or without direct contact with thetarget site structure. For example, the neurostimulation may beperformed using a probe that transmits electromagnetic energy (e.g., RF)that is captured by the target site.

In some instances, the neurostimulation is applied while the targetsubject is performing a task. A neurostimulation waveform is selectedbased on the task that is being performed. Without intending to be boundby theory, it is believed that applying neurostimulation in this mannerwill facilitate rehabilitation by enhancing the natural process ofneural plasticity.

In certain embodiments, the method includes a process for providingphysiologic feedback regulation. In some instances, the method furthercomprises sensing a bodily activity in the target subject. The bodilyactivity to be sensed by the sensor is any characteristic or function ofthe body including bodily organs, such as mechanical, motion,electrical, or chemical activity and includes, for example,gastrointestinal function including gastric acid, intestinal motility,and peristalsis; temperature; respiratory function; heart rate;capillary pressure; venous pressure; perfusion; blood gases such ascarbon dioxide including partial pressure of carbon dioxide; oxygenationincluding blood oxygenation levels, oxygen saturation levels partialpressure of oxygen, oxygen consumption, oxygen pressure; water pressure;nitrogen pressure; carbon dioxide pressure in the tissue; circulation(including blood and lymphatic); electrolyte levels in thecirculation/tissue; diffusion or metabolism of various agents andmolecules (such as glucose); neurotransmitter levels; body temperatureregulation; blood pressure; blood viscosity; metabolic activity;cerebral blood flow; pH levels; vital signs; galvanic skin responses;perspiration; electrocardiogram; electroencephalogram; action potentialconduction; chemical production; body movement including limb movement,posture, and gait; response to external stimulation; cognitive activity;dizziness; pain; flushing; motor activity including muscle tone; visualactivity; speech; balance; diaphragmatic movement; chest wall expansion;concentration of certain biological molecules/substances in the bodysuch as, for example, glucose, liver enzymes, electrolytes, hormones,creatinine, medications, concentration of various cells, platelets, orbacteria. These bodily activities can be measured utilizing a variety ofmethods including but not limited to chemical analysis, mechanicalmeasurements, motion sensors, laser, and fiber-optic analysis.

In response to the bodily activity sensed, the output waveform can beinitiated or adjusted to affect the bodily activity. For example, thebodily activity being sensed may be gastric pH levels. In response tothe gastric pH level, the output waveform can be initiated or adjustedto affect the gastric pH production. In another example, the bodilyactivity being sensed may be heart rate. In response to an abnormalheart rate, the output waveform can be initiated or adjusted to affectthe heart rate. In another example, the bodily activity being sensed maybe limb motion. In response to a tremor in the limb, the output waveformcan be initiated or adjusted to reduce the tremor.

Various types of adjustments can be made to the output waveform. Forexample, the waveforms may be modified to have a different pattern,intensity, amplitude, frequency, duration, pulse width, or number ofpulse trains. In another example, additional pulses may be added to thewaveform. The additional pulses may be added within the waveform orbetween waveforms. The additional pulses may be at pre-determinedpositions in the waveform, at pre-determined intervals, or triggered bya spike in the waveform. In another example, the waveforms may bemodified by copying, cutting, pasting, deleting, cropping, appending, orinserting desired segments of waveforms. In another example, theneurostimulation may be adjusted by selecting another waveform from alibrary of waveforms.

The present invention can be used to treat a variety of conditions ordisorders. Non-limiting examples of medical conditions that can betreated according to the present invention include genetic, skeletal,immunological, vascular or hematological, muscular or connective tissue,neurological, ocular, auditory or vestibular, dermatological,endocrinological, olfactory, cardiovascular, genitourinary,psychological, gastrointestinal, respiratory/pulmonary, neoplastic,inflammatory medical conditions or any suitable combination thereof.Further, the medical condition can be the result of any etiologyincluding vascular, ischemic, thrombotic, embolic, infectious (includingbacterial, viral, parasitic, fungal, abscessal), neoplastic,drug-induced, metabolic, immunological, collagenic, traumatic, surgical,idiopathic, endocrinological, allergic, degenerative, congenital,abnormal malformational causes or suitable combinations thereof.

With respect to treating neurological medical conditions, such medicalconditions can involve any medical conditions related to the componentsof the nervous system such as, for example, the brain including thecerebellum, brain stem, pons, midbrain, medulla; the spinal cord;peripheral nerves; peripheral ganglia; and nerve plexuses. Non-limitingexamples of neurological conditions include neurodegenerative disorders,Alzheimer's disease, epilepsy, multiple sclerosis, ALS, Guillan Barre,neurovascular disorders including stroke, cerebral palsy, intracerebralhemorrhage, dementia, vertigo, tinnitus, diplopia, cerebral vasospasm,aneurysm, atriovenous malformation, brain malformations, movementdisorders, multi-system atrophy, olivopontocerebellar degeneration,familial tremor dystonia including cervical dystonia, torticollis,facial dystonia, blepharospasms, spasmodic dysphonia, radiculopathy,neuropathic pain, sleep disorders, disorders of temperature regulationin the body and extremities, postherpetic neuralgia involving the face,head, body or extremities. The neuropathic pain may be caused byfracture, crush injury, compressive injury, repetitive movement injury,diabetes, trauma, alcohol, infection, or hereditary. The sleep disordermay be sleep apnea, restless leg syndrome, narcolepsy, snoring,insomnia, drowsiness, or suitable combinations thereof.

Non-limiting examples of movement disorder include or manifest as:ataxia, akinesia, athetosis, ballismus, hemiballismus, bradykinesia,dystonia, chorea including Huntington's disease, multiple systematrophies (e.g., Shy-Drager syndrome), myoclonus, Parkinson's disease,progressive supranuclear palsy, restless leg syndrome and periodic limbmovement disorder, tics, Tourette's syndrome, tremor (e.g., essentialtremor, resting tremor), Wilson disease, tardive dyskinesia, andparalysis or weakness due to stroke or other cortical injury.

In another aspect, the present invention provides a stimulation systemfor neuromodulation using waveform signals. Turning to the figures, FIG.1 depicts a stimulation system 10 that can be implemented according toan aspect of the present invention. The stimulation system 10 includesmemory 12 that stores (or records) waveform data corresponding to one ormore waveforms. The waveform data can be stored in the memory 12 basedon an INPUT signal received by a communication system 14. The one ormore waveforms can be stored as one or more complete periods of thewaveform, which can be referred to as snippets. As described herein, thewaveform data that is stored in the memory 12 corresponds to one or moreactual waveforms, which can be an analog or digital representation ofthe waveform(s). This type of waveform data that is stored in the memory12 thus is referred to herein as non-parametric waveform data.

The communication system 14 can include a receiver that receives theINPUT signal via one or more communication modes, such as includingradio frequency (RF), infrared (IR), direct contact (e.g., electricallyor optically conductive path), capacitive coupling, and inductivecoupling to name a few. The INPUT signal further can be provided viamore than one communication mode, such as providing the INPUT signal asincluding one or more waveforms via one mode and command information(e.g., scheduling and programming information) via another mode. Thecommunication system 14 can be capable of bi-directional communications,such as also including a transmitter or transceiver circuitry. Thetransmitter and receiver portions of the communication system 14 canemploy the same or different communication modes.

The memory 12 can be implemented as an analog memory, such as is capableof storing an analog version of the waveform that is received by thecommunication system 14. The memory can also be implemented as digitalmemory that stores a digital representation or sample of the inputwaveform or stores a digitally encoded version of the waveform. Forinstance, the memory 12 can store the sample waveform as a digitalsample, such as using pulse code modulation (PCM) or adaptivedifferential pulse code modulation (ADPCM) or pulse width modulation(PWM), although other modulation techniques can be utilized. The digitalsample of the waveform further may be stored in a compressed formataccording to one or more CODECs (e.g., MP3, AAC, 3GPP, WAV, etc.),although compression is not required. There are a multitude of varyingstandards that can be grouped in three major forms of audio CODECs,including, for example, direct audio coding, perceptual audio coding,and synthesis coding, any one or more of which can be employed to storea digital representation of waveforms in the memory 12.

A playback system 16 is configured to retrieve and play back one or morewaveforms according to selected waveform data stored in the memory 12.The playback system 16 can be implemented as hardware (e.g., one or moreintegrated circuits), software or a combination or hardware andsoftware. The implementation of the playback system 16 can vary, forexample, according to the type of audio (analog or digital) that isstored in the memory 12. The playback system 16, for example, can beprogrammed with one or more audio CODECs that convert (or decode) theencoded waveform data into a corresponding output waveform.

The playback system 16 can be implemented as an integrated circuit 24,such as including a microcontroller or microprocessor. For instance,suitable microcontroller integrated circuits (ICs) are commerciallyavailable from Atmel Corporation of San Jose, Calif. Suchmicrocontroller ICs may include the memory 12 integrated into the IC 24,such as in the form or FLASH memory or other programmable memory(electrically programmable read only memory (EPROM)), or the memory 12can be external to the IC 24.

The playback system 16 provides the output waveform to an amplifier 18that amplifies the output waveform. The playback system 16 further canbe configured to provide output waveforms to one or more outputchannels, each output channel providing an amplified output waveformcorresponding to the waveform data stored in the memory 12. One or moreelectrodes 20 can be coupled to each of the channels for deliveringelectrical stimulation to biological tissue located adjacent theelectrode(s).

As an example, the playback system 16 can be configured to select one ormore waveforms from the memory 12 for providing a corresponding outputwaveform. As mentioned above, a plurality of different types ofwaveforms can be stored in the memory 12, generally limited only by thesize of the memory. The playback system 16 thus can select and arrangeone or more waveforms to provide a desired output waveform pattern.Additionally, the playback system 16 further can combine a plurality ofdifferent waveforms into more complex composite output waveforms. Itwill be appreciated that the ability of selecting from a plurality ofpredefined stored waveforms affords the stimulation system enhancedcapabilities, as virtually any output waveform can be stored and playedback from the memory 12.

The design can be simplified even further by storing waveforms ofgradually changing parameters in the memory 12. For example, a pluralityof versions of the same waveform, but of varying amplitude, can bestored in the memory 12 so as to effectively eliminate the need foradditional amplitude controlling circuitry. Accordingly, if a greater orlesser amplitude may be required for a given application, an appropriatedifferent waveform can be selected. The playback system 16 can also beprogrammed and/or configured to manipulate one or more selectedwaveforms from the memory 12, such as using digital or analogcomputation, to vary parameters (e.g., amplitude, frequency, phasesymmetry and/or duty cycle) of the one or more selected waveforms. Thecorresponding amplified output signal corresponds to an amplifiedversion of the selected waveform, including any such manipulations.

The amplifier 18 can be implemented as an analog amplifier or a digitalamplifier. For an analog version of the amplifier 18, adigital-to-analog converter (not shown) can provide a correspondinganalog version of the output waveform and a linear amplifier, in turn,can operate to amplify the analog output waveform to a desired level.Power conditioning circuitry can be utilized to provide a desiredpotential for use in generating the amplified output waveform.Alternatively, the amplifier can be implemented as a class D amplifier(or switched power supply), although other amplifier topologies can alsobe used. By implementing the amplifier as a class D amplifier, theamplifier 18 can run directly off a battery or other power supplyefficiently and be implemented using low-voltage components. Thoseskilled in the art will appreciate various types of switching amplifiertopologies are that can be utilized in the system 10. Additionally, theamplifier 18 can be configured to operate in a current mode or a voltagemode control, such as to provide a desired current or voltage.

The amplifier 18 can comprise a network of amplifiers arranged to drivea plurality of loads (depicted as electrodes 20) according to respectiveoutput waveforms provided by the playback system 16. The electrode(s) 20can be implanted in strategic locations in the body of subject 30according to given application of the stimulation system 10. Forexample, the electrode(s) can be located within the brain, spinal cordor other anatomic locations. The anatomic locations can be in closeproximity to the playback system or at remote locations.

The system 10 can be implemented as an open loop system or a closed loopsystem. For the example of a closed loop system, the system 10 can alsoinclude feedback, indicated as dotted line 22. The feedback 22 providesinformation about the stimulus being applied to the electrode(s) and/orabout a characteristic of the electrode(s). As an example, the feedback22 can provide an electrical signal to the playback system 16, based onwhich an indication of load impedance associated with the electrode(s)can be determined.

The impedance characteristics can be utilized for a variety of purposes.For instance, the impedance can be employed to implement currentcontrol, such as by the playback system 16 selecting a predefinedwaveform from the memory 12 to maintain a desired current level in thewaveform that is provided to the electrode(s) 20. Alternatively oradditionally, the impedance characteristics can be used as part ofdiagnostics, such as by recording (or logging) impedance over extendedperiods of time and evaluating a condition of the electrode(s). Asanother alternative, the feedback 22 can be employed to ascertain highimpedance conditions (e.g., an open circuit) or a low impedancecondition (e.g., a short circuit). Those skilled in the art willunderstand and appreciate various approaches that can be implemented toprovide the feedback 22. Additionally, various types of diagnostic oroperational controls can be implemented based on such feedback.

Since the waveform is played back from non-parametric waveform data thatis stored in the memory 12, the system 10 can be implemented in a costefficient manner from commercially available recording and playbackcircuitry. Additionally, because the waveforms can be generatedexternally, provided to the system 10, and stored in the memory 12,there is a greater degree of flexibility in the types and complexity ofwaveforms that can be stored in the memory. That is, the system 10 isnot constrained by limitations in the cost or size or complexity of atypical parametric waveform generator. Additionally, the playback system16 may further construct more complex waveforms by combining two or morestored waveforms in a particular order (e.g., a pattern of waveformtrains). As an example, one or more of the waveforms stored in thememory can include actual recorded impulses (electrical waveforms), suchas can be recorded from the patient in which the stimulation system 10is to be implanted, from a different person or from a non-human animalsubject. The playback system 16 can also combine two more waveforms byperforming a superimposition of such waveforms to construct a desiredaggregate waveform.

In certain embodiments, stimulation system 10 further includes a sensor80 to provide physiologic feedback regulation. Sensor 80 is located onor within the body of subject 30 and detects mechanical, motion,electrical, and/or chemical activity. Sensor 80 may be located withinthe target site, proximal to the target site, or distal to the targetsite, whether in or outside the nervous system. Examples of electricalactivity that can be detected by sensor 80 include neuronal electricalactivity, such as the electrical activity characteristic of thesignaling stages of neurons (i.e. synaptic potentials, trigger actions,action potentials, and neurotransmitter release) at the target site andby afferent and efferent pathways and sources that project to and fromor communicate with the target site. For example, sensor 80 can measure,at any signaling stage, neuronal activity of any of the extensiveconnections of the target site. In particular, sensor 80 may detect therate and pattern of the neuronal electrical activity to determine theelectrical signal to be provided to the lead. Examples of chemicalactivity detected by sensor 80 located within or proximal to the targetsite include measurements of neuronal activity, such as the modulationof neurotransmitters, hormones, pro-hormones, neuropeptides, peptides,proteins, electrolytes, or small molecules by the target site andmodulation of these substances by afferent and efferent pathways andsources that project to and from the target sites or communicate withthe target sites. With respect to detecting electrical or chemicalactivity in the nervous system, sensor 80 could be placed in the brain,the spinal cord, cranial nerves, and/or spinal nerves. For example,sensor 80 could be placed in the intralaminar nuclei to sense neuronalelectrical activity. In certain embodiments relating to treatingmovement disorders, the activity in the intralaminar nuclei is sensed.Sensor 80 placed in the brain is preferably placed in a layer-wisemanner. For example, sensor 80 could be placed on the scalp (i.e.electroencephalogram), in the subgaleal layer, on the skull, in the duramater, in the sub dural layer and in the parenchyma (i.e. in the frontallobe, occipital lobe, parietal lobe, temporal lobe) to achieveincreasing specificity of electrical and chemical activity detection.Sensor 80 could measure the same types of chemical and/or electricalactivity within or proximal to the target site as described above. Withrespect to detecting mechanical, motion, electrical, or chemicalactivity by sensor 80 located outside the nervous system, sensor 80 maybe placed in venous structures and various organs or tissues of otherbody systems, such as the endocrine system, musculoskeletal system,respiratory system, circulatory system, urinary system, integumentarysystem, and digestive system or such sensors may detect signals fromthese various body systems. For example, sensor 80 may be an externalsensor such as a pulse oximeter, or an external blood pressure, heart,and respiratory rate detector. In another example, sensor 80 may bemotion detectors attached to a body limb for detecting tremors, abnormalgait, or other abnormal movement. All the above-mentioned sensingsystems may be employed together or any combination of less than allsensors may be employed together.

Sensor 80 sends a sensor signal conveying information about the bodilyactivity to stimulation system 10. In response to the sensor signal,stimulation system 10 initiates or adjusts the application of thewaveform neurostimulation to the target site to affect the bodilyactivity. In certain embodiments, the signal from sensor 80 is incommunication with a controller 92, which receives the signal andcontrols the output of neurostimulation to the target site. The signalfrom sensor 80 may be transmitted via a transmission line (e.g., anelectrical or optical connection) or via wireless communication (e.g.,radio-frequency, infrared, or ultrasound). Controller 92 may be incommunication with and control various components of system 10 toinitiate or adjust the neurostimulation applied by electrode 20. Forexample, controller 92 may control communication system 14, memory 12,playback system 16, and/or integrated circuit 24. In the embodiment ofFIG. 1, controller 92 is internal to the body of subject 30. However, inalternate embodiments, controller 92 is external to the body of subject30.

FIG. 2 depicts an example of a programmable stimulation system 50 thatcan be implemented according to an aspect of the present invention. Thesystem 50 comprises an implantable pulse generator (IPG) 52 that isimplanted in the body of a subject 30. The IPG 52 can be implanted invarious locations, such as under the skin of the chest (e.g., below thecollarbone) or other anatomic location. In contrast to many existing IPGdesigns, the IPG 52 is not required to generate a pulse or waveform, butinstead is configured to play back one or more predefined waveforms. TheIPG 52 includes an internal receiver 56 that can receive a signal froman external programmer 58, which is located external to the body ofsubject 30. The external programmer 58 can communicate the signal to thereceiver 56 using one or more communications modes, such as describedherein. In the example, of FIG. 2, a connectionless communications modeis illustrated, although a physical connection can be made to provide anelectrical or optical conductive medium for data communications.

A waveform generator 60 can provide one or more waveforms 62 to theexternal programmer 58 for transmission to the IPG 52. The waveformgenerator 60 can include any type of device or system that can generatethe one or more waveforms 62, including a programmable signal generator,a pulse generator, and a waveform synthesizer to name a few. Thewaveform generator 60 further may be a PC-based system or a stand alonesystem capable of generating one or more desired waveforms. The waveformgenerator 60 can also be programmed with biological, recorded waveforms,such as may have been measured and recorded from the body of subject 30or from any other biological subject (e.g., human or other animal).

For electrical stimulation of a patient's brain, the waveform can berecorded as electrical impulses measured from one or more anatomicalregions of a biological subject's brain. The waveform generator 60 thuscan provide the biological, recorded waveforms to the externalprogrammer 58 for transferring such waveforms to the memory via theinternal receiver 56 of the IPG 52. The measurements, for example, canbe made by sensing electrodes inserted within target tissue or byexternal sensors placed adjacent target tissue or a combination ofinternal or external sensors. Those skilled in the art will understandand appreciate various types of sensors and measurement devices that canbe employed to measure and record the biological waveforms.Additionally, while the foregoing mentions recording electrical impulsesfrom one or more regions of a subject's brain, it is to be appreciatedthat the impulses can be recorded from other nerve tissue, one or moreother organs, or other anatomical sites (human or other animal) or anycombination thereof.

The external programmer 58 transmits a signal 59 to the receiver 56 ofthe IPG 52 corresponding to the waveform 62 provided by the generator60. As discussed herein, the signal 59 transmitted by the externalprogrammer 58 can include (or encode) the actual waveform 62 provided bythe waveform generator 60 (e.g., an actual biological, recorded waveformor a synthesized waveform). The external programmer can transmit thesignal 59 as including a complete period, more than one period (e.g.,snippets) or as a fraction of a period of the desired waveform 62 in anycommunications mode. The receiver 56, for example, can provide thewaveform to the memory as encoded waveform data, such as correspondingto an encoding scheme implemented by the waveform generator 60.Alternatively, the receiver 56 can demodulate/decode an encoded receivedsignal and provide a corresponding demodulated/decoded signal 66 to thememory 64 so that the waveform data corresponds to the one or morewaveforms 62. Additionally encoding may also be performed by thereceiver 56 or other circuitry (not shown) for providing encodedwaveform data for storing the waveform(s) 62 the memory 64.

The sample of the waveform 66 stored in the memory 64 can correspond toan analog version of the waveform or a corresponding digital (e.g., PCM)representation of the waveform. Those skilled in the art will appreciatevarious different representations that can be stored in the memory 64based on the teachings contained herein. It will further be understoodthat some or all of the waveforms 66 stored in the memory 64 can beprogrammed prior to implantation of the IPG 52 within the body ofsubject 30.

After a desired number of one or more waveforms 66 have been stored inthe memory 64, such as during a program mode, playback circuitry 68 canplay back one or more selected waveforms 66 from the memory 64. Theplayback circuitry 68 can play back a waveform according to a definedplay back schedule, which may be a periodic or continuous schedule.Alternatively or additionally, the playback circuitry 68 can beconfigured to play back one or more selected waveforms in response to astimulus, which stimulus can be user-generated or provided by associatedsensing circuitry (not shown).

The playback circuitry 68 can play back the one or more selectedwaveforms by retrieving the selected waveform(s) from the memory andproviding the output waveform(s) to one or more amplifiers 70. Theamplifier 70 amplifies the output waveform to a desired level to providea corresponding amplified version of the waveform. That is, theamplified waveform 72 can be substantially the same as the waveform 62generated by the waveform generator 60. Alternatively, when the waveform62 is stored as encoded data, the amplified waveform 72 can correspondto a decoded version of the waveform. Typically, a plurality ofwaveforms 66 are stored in the memory 64 to provide a greater selectionof available waveforms for operating the IPG 52. The amplified waveform72 can be provided to one or more strategically placed electrodes orother implantable devices capable of delivering an electrical stimulusto adjacent biological tissue.

In certain embodiments, stimulation system 50 further comprises a sensor80 to provide physiologic feedback regulation. In the embodiment shownin FIG. 2, sensor 80 is in communication with a controller 90 that isexternal to the body of subject 30. Controller 90 is in communicationwith and controls external programmer 58 to initiate or adjust theneurostimulation. In alternate embodiments, controller 90 is internal tothe body of subject 30 and/or controls other components of stimulationsystem 50.

FIG. 3 depicts an example of another implantable pulse generator (IPG)system 100 that can be implemented according to an aspect of the presentinvention. The IPG system 100 is configured to deliver electricalstimulation to target tissue, such as by using one or more electrodes.In the example of FIG. 3, IPG the system 100 includes a control system102 that is operative to control recording and playback of one or morewaveforms for implementing electrical stimulation. The control system102 can be implemented as a microcontroller unit (e.g., an integratedcircuit) or as a combination of one or more integrated circuits that canbe programmed and/or configured to implement the functions describedherein.

The control system 102 is coupled to a transceiver 104. The transceiver104 can be coupled to an antenna 106 for implementing wirelesscommunications to and from the IPG system 100. As used herein, the term“wireless” refers to communication of information without a physicalconnection for the communication medium (the physical connection usuallybeing electrically conductive or optical fiber). As described herein,the transceiver 104 alternatively could be implemented as a hard wiredconnection (e.g., electrically conductive or optical links). Thoseskilled in the art will understand and appreciate various types ofwireless communication modes that can be implemented by the transceiver104, such as described herein. As an example, the transceiver 104 can beprogrammed and/or configured to implement a short range bi-directionalwireless communication technology, such as Bluetooth or one of the802.11x protocols.

The transceiver 104 can also employ security features to inhibitunintentional or unauthorized access to the IPG 100. The securityfeatures can be implemented as software and/or hardware, such may bepart of the transceiver and/or as part of the control system 102. As oneexample, the security measures can be integrated as part of the wirelessprotocol implemented by the transceiver 104 (e.g., Bluetooth wirelesscommunications employs the SAFER+ algorithm for authentication and keygeneration). Other communication protocols may employ different securitymeasures to mitigate unauthorized communication with the IPG.Alternatively or additionally, the transceiver 104 can utilize apredefined key or ID associated with the IPG 100 to identify theintended recipient of the communication and confirm the receivedinformation as originating from an authorized or trusted source.

The control system 102 is connected to provide one or more outputwaveforms to an amplifier system 108. The amplifier system 108 isconnected to receive and amplify the output waveforms from the controlsystem 102 and provide the corresponding amplified waveforms to anoutput system 110. The output system 110 is configured to distribute theamplified waveforms to a set of one or more corresponding outputchannels 112. The output channels 112 may include output portselectrically coupled directly with respective electrodes or otherperipheral devices coupled to receive the output waveforms from the IPGsystem 100. The IPG system 100 can also include a power system 114 thatis operative to supply power for operation of the various components.

Turning to the contents of the control system 102, the control system102 includes memory 116 that can store digital data representing each ofthe one or more waveforms. The memory 116 can be implemented as randomaccess memory (RAM), flash memory, programmable read-only memory (PROM),electrically erasable programmable read-only memory (EEPROM) or othertypes of memory capable of storing digital representations of the one ormore waveforms. The storage capacity of the memory 116 may varyaccording to application design requirements of the IPG 100.

A central processing unit (CPU) 118 is coupled to the memory 116, suchas via a bus 120. The bus 120 can be any type of connection or backplane(or a combination thereof) that enables communication between thevarious components of the control system 102, including the memory 116and the CPU 118. For example, the CPU 118 and memory 116 can beinstantiated on an integrated circuit, such as a microcontroller orapplication specific integrated circuit (ASIC) that forms the controlsystem 102. In such an embodiment, the bus 120 can be implemented as aninternal IC bus. While the memory 116 is depicted as residing within thecontrol system 102, at least a portion of the memory could beimplemented as an external memory structure (e.g., implemented as one ormore integrated circuits).

The CPU 118 can selectively retrieve the respective waveforms from thememory 116 and supply (or play back) the selected retrieved waveform tothe amplifier system 108. As an example, the CPU 118 can performcomputer-executable control instructions that control which of the oneor more waveforms are supplied to the amplifier system 108. Theexecutable instructions can also control or adjust parameters of theoutput waveforms. The computer-executable control instructions can bestored in the memory 116, such as with the waveform data. The controlsystem 102 can also include one or more digital-to-analog converters(DAC) 122 and 124 that are connected with the bus 120. The CPU 118 thuscan supply the retrieved waveform data to the DACs 122 and 124. The DACs122 and 124 can convert the stored digital waveforms to correspondinganalog output waveforms and provide the analog output waveforms theamplifier system 108.

The CPU 118 can also employ computer executable instructions (such asmay be stored in the memory 116) to control operation of the transceiver104. The CPU 118 can communicate with the transceiver 104 through thebus 120 through a corresponding interface 126 that is connected betweenthe transceiver and the bus. As an example, during a programming mode,the CPU 118 can receive and send information via the transceiver 104 forprogramming the memory 116. The information received, for example, mayinclude more digital waveforms that are stored in the memory for playback during a normal operating mode.

The information received via the transceiver 104 can also includecomputer-executable instructions such as for control operatingparameters of the IPG 100. Alternatively, some or all of the IPGoperating parameters can be pre-programmed. The programmable operatingparameters can include scaling parameters for adjusting one moreparameters of the output waveform. For example, the scaling parameterscan include the amplitude, pulse width, pulse duration, as well ascontrol the number of pulse trains of the one or more stored waveformsthat are supplied as the corresponding analog output waveform to theamplifier system 108. The CPU 118 can modify such scaling of parametersduring operation to provide a modified version of the stored waveform(e.g., the modifications being based on feedback 144 to provide forclosed loop operation).

The CPU 118 can also control which of the plurality of output channels112 are provided with corresponding output waveforms. For example, theCPU 118 can provide a CONTROL (or selection) signal 132 to the outputsystem 110 through the bus 120 and via a corresponding interface 130.The output system 110 can be implemented as a switching matrix ormultiplexer that is configured to selectively couple selectedcorresponding output signals from the amplifier system 108 to thecorresponding output channels 112 based on the CONTROL signal. Forinstance, the output system 110 can include network of switches that areconfigured to complete an electrically conductive path from the controlsystem to the selected output channel(s). The output system 110 thus canselectively distribute output waveforms to one or more of the outputchannels 112 based upon the control instructions stored in the memory116 that define how such distribution is to occur.

As described herein, an electrode (or electrodes) can be coupled to eachof the corresponding output channels 112 for delivering correspondingelectrical stimulus based on the amplified analog waveforms distributedto the corresponding outputs by the output system 110. The size and theconfiguration of the output system 110 can vary according to the numberof output channels as well as the number of respective inputs providedby the amplifier system 108.

The amplifier system 108 can include a plurality of amplifiers, which inthe example of FIG. 3 are depicted as including four amplifiers(indicated at AMP 1 through AMP 4). As mentioned above, the controlsystem 102 includes DACs 122 and 124 that provide corresponding analogoutput waveform signals to the amplifier system 108. In the example ofFIG. 3, the DAC 122 is coupled to supply a corresponding analog inputtwo amplifiers AMP 1 and AMP 2. The DAC 124 is coupled to provide acorresponding output signal to the amplifier AMP 4. The control system102 also provides the corresponding signal indicated at 132 forselecting which of the output waveforms is connected to supply theanalog input to the amplifier AMP 3. For the example of FIG. 3, in whichthere are two analog outputs provided by the control system 102, thecontrol system 102 can provide an output that controls operation ofcorresponding switches 134 and 136. The output thus can operate toconnect the output of DAC 122 with the amplifier AMP 3 or to connect theoutput of DAC 124 with the input of AMP 3. Those skilled in the art willunderstand and appreciate various other types of circuits and switchnetworks that can be utilized to supply a desired output waveformselectively to the input of amplifier AMP 3. Such circuitry can alsoinclude an inverter to supply an inverted version of a stored waveform,for example.

To mitigate interference between the respective output channels 112, DCblocking capacitors 138 can be connected between the output system 110and the corresponding ports of the output channels 112. The DC blockingcapacitors 138 can be selected to have a corresponding capacitance basedupon the desired frequency range at which the output signals are to besupplied to the corresponding output channels 112.

The power system 114 includes a battery 140 that stores a charge forproviding corresponding DC voltage to the IPG system 100. For example,the battery 140 supplies the DC output voltage to an associated powersupply system 142. The amount of voltage provided the battery 140 canvary according to the power requirements of the IPG system 100.

The power supply system 142 can also include load tracking and switchmode power supplies for providing appropriate power to the various partsof the IPG system. As an example, the load tracking aspect of the powersupply system 142 can vary the voltage rails supplied to the outputsystem 110 as a function of the particular output waveform(s) beingprovided by the control system 102 to the amplifier system 108.

Additionally or alternatively, the control system 102 can vary thevoltage rails of the output system 110 according to IPG powerrequirements, such as by controlling the power supply system 142. Thecontrol system 102 can also vary the amplitude of the analog outputwaveform by controlling a variable gain of the respective amplifiers.Alternatively, as described herein, digital waveforms stored in thememory 116 can be preprogrammed with different desired amplitudes. Thus,to provide the desired amplitude at a given channel, the control system102 can play back the given waveform that has the desired amplitude.

The output system 110 can also provide feedback, indicated at 144, tothe control system 102. The feedback 144 can be sent over one or moreconnections depending on the extent of information being provided. Inthe example of FIG. 3, the feedback 144 can include a plurality ofinputs, each being provided to the analog digital converter ADC 146. TheCPU 118 can receive a corresponding digital representation of thefeedback signals received ADC 146. For instance, the digital feedbackinformation can be stored in memory 116 for use by one or more controlfunctions that are being executed by the CPU 118.

The CPU 118 (running executable instructions) can evaluate thecorresponding digital representation of the feedback signals toascertain information about the operation of the IPG 100. As oneexample, the feedback 144 can provide an indication of the outputimpedance for the respective output channels (e.g., including theimpedance of the electrodes connected at the respective outputchannels). The CPU 118 or other circuitry can determine the impedance,for example, as a function of the voltage or current signal provided bythe feedback 144. The determined impedances can be used for a variety offunctions.

By way of example, the control system 102 can implement safety functionsbased on the detected impedance at the respective output channels 112.For instance, if the digitally converted feedback information indicatesa sufficiently low impedance (e.g., corresponding to a short circuitcondition at one or more output channels 112) the CPU 118 can implementpre-programmed control procedures. Additionally, if the impedanceinformation provided by the feedback 144 indicates a sufficiently highimpedance (e.g., corresponding to an open circuit condition), suitableprocedures may be implemented. A high impedance condition may indicatethat an electrode has been decoupled from its output channel. Duringoperation, in response to detecting an impedance that is outside normaloperating parameters, the control system 102 can, for example, adjustand/or discontinue providing output waveforms to one or more of theoutput channels 112 at which the condition has been detected.

As another example, the feedback 144 can provide an indication of chargeassociated with the output channels. For example, the feedback 144 caninclude an indication of voltage and current characteristics for each ofthe output channels 112. The control system 102 can be programmed (e.g.,with appropriate executable instructions stored in the memory 116) tocompute a charge density value based on input parameters and knownelectrical characteristics of each output channel. If the computedcharge density for a given output channel 112 exceeds a predeterminedthreshold, the control system 102 can deactivate the given outputchannel.

Still another example might be to program the control system 102 toperform charge balancing associated with operation of the amplifiersand/or the output system 110 based on the feedback 144. For example, thecontrol system 102 can monitor the charge at a given output channel suchas to help ensure that no net DC voltage exists in any of the channels112 that might be adverse to the desired electrical stimulation beingprovided at each channel.

The control system 102 can also activate the transceiver 104 fortransmitting appropriate information when the feedback 144 indicatesthese and other sensed conditions may reside outside of expectedoperating parameters. The control system 102 can initiate transmissionof the information automatically in response to detecting operationoutside of expected operating parameters. Alternatively, the controlsystem 102 can store such information (e.g., in the memory 116) andtransmit in response to being interrogated by a corresponding externaltransmitter or external transceiver.

The feedback 144 can also provide an indication of the available energyin the battery 140. Accordingly, one or more of the inputs in thefeedback 144 can be converted to a corresponding digital representationand evaluated by the CPU 118. If the available battery power falls belowa predetermined threshold, for example, appropriate action can be takento conserve power or otherwise provide an indication (e.g., via thetransceiver 104) that the battery 140 should be replaced or recharged.

The power system 114 can also include a battery charging system 148 anda power receiver 150. The battery charging system 148, for example, mayinclude charging control circuitry for the battery 140 as well as apower converter (e.g., including a rectifier) that is operative toconvert the power received by the power receiver 150 to an appropriateform and level to facilitate charging the battery 140. In this regard,the battery 140 can be a rechargeable type, such as a lithium battery,or nickel cadmium battery capable of extended use between charges.Alternatively, as described herein, the battery 140 may be replaceable.

The power receiver 150, for instance, can be implemented as a inductivepower pick-up such as including an inductive coil and other appropriatecircuitry that can receive, filter and couple power (e.g., via mutualinductance) from a corresponding power transmitter that may be placedadjacent or in contact with the power receiver. The power receiver 150and the battery charging system 148 can be implemented as an integratedsystem to facilitate charging the battery 140. Additionally, the controlsystem 102 can control the battery charging system 148 in response tothe feedback 144. For example, the control system 102 can providecorresponding control signals 151 to the battery charging system 148through a corresponding interface 152. Additionally, the current and/orvoltage associated with the charging of the battery (or other parametersassociated with operation of the charging system) can be monitored bythe control system 102 via one or more corresponding analog inputs 154that is provided to the ADC 146. The control system 102 can control thebattery charging process in response to the voltage and/or currentcharacteristics associated with the charging process, as detected viathe input 154.

FIG. 4 depicts another example of an IPG system 200 according to anembodiment of the present invention. The IPG system 200 includes asystem control block 202. The system control 202 is programmed and/orconfigured to control basic operation of the system 200. The basicoperation can include power management, communication and outputcontrols. The system control 202 can also program one or more waveformcontrollers 204. As described herein, each of the waveform controllers204 include memory 206 that can store waveform data representing one ormore waveforms.

In the example of FIG. 4, there are M waveform controllers 204(indicated at WAVEFORM CONTROLLER 1 through WAVEFORM CONTROLLER M),where M is a positive integer. Each waveform controller 204 isprogrammed to retrieve one or more waveform from its respective memory206 for playback over one or more output channels 208. For example,there are N output channels, where N is a positive integer where N≧1. Asone example, N=M; although, N may not be equal to M (e.g., N>M or N<M).

An amplifier 210 can be connected to drive each of the respective outputchannels 208. FIG. 4 depicts a separate amplifier 210, indicated at AMP1, AMP 2 through AMP N, for driving each of the respective N outputchannels 208. Additionally, each amplifier 210 can be connected to arespective output channel through a DC blocking capacitor 211 to reduceinter-channel interference. By way of example, each of the amplifiers210 can drive its associated output channel 208 based on a set of one ormore waveform signals provided by one or more of the waveformcontrollers 204.

Each waveform controller 204 can include an output system 212 thatcontrols to which of the N output channels 208 each respective waveformcontroller 204 provides its output waveform signal. The output system212 thus selectively distributes output waveform signals to one or moreoutput channels, such as based on a selection signal (not shown). Forinstance, each output system 212 can be electrically connected with aninput of each of the N amplifiers 210 through a connection matrix 214.The connection matrix 214 may include a set of connections (e.g.,electrically conductive wires or traces) that directly connect each ofthe M waveform controllers 204 and each of the N amplifiers.Alternatively, the connection matrix 212 can provide for a selectedsubset of connections from the waveform controllers to the amplifiers210. Each amplifier 210 may include the same or a different number ofinputs.

In some cases, a given amplifier 210 may receive an input waveform fromonly a single waveform controller 204. However, the design of FIG. 4affords flexibility in which the given amplifier 210 can receive outputwaveforms from more than one waveform controller 204. For example, thesystem control 202 can provide instructions to each of the waveformcontrollers 204 to control to which set of one or more amplifier 210 thewaveform controller provides its output waveform. Additionally, thesystem control 202 can program which respective waveform (either asingle wave or train of multiple waveforms) are to be provided by eachof the waveform controllers 204 to the respective amplifiers.

To support multiple input waveforms, the amplifiers 210 can include aninput stage (e.g., summing circuitry—not shown) that aggregates theinput waveforms received via the connection matrix 214. Each of theamplifiers 210 thus can overlay multiple waveforms received from thewaveform controllers 204 to form a composite waveform that is, in turn,amplified and provided to the corresponding output channel 208.

The amplifiers 210 can also provide feedback, indicated schematically at216, to the waveform controllers 204. For example, the feedback 216 canprovide an indication of impedance for the respective output channels208. The waveform controllers 204 can employ the impedance to ascertainwhether the system 200 is operating within expected operating parameters(e.g., for placement of an electrode or for implementing safetyfeatures), such as described herein. The waveform controllers 204 canimplement appropriate action based on the feedback received, includingadjusting an output waveform or even terminating an output waveform frombeing provided to one or more of the amplifiers 210. The waveformcontrollers 204 can also provide information to the system control 202based on the feedback 216.

As another example, the feedback 216 can provide an indication of chargeassociated with the electrode(s) being driven by a given amplifier 210.The waveform controller 204 can be programmed to compute charge densitybased on input parameters and known electrical characteristics of theelectrode devices connected to the respective output channels 208. Ifthe charge density exceeds a predetermined threshold, the waveformcontroller 204 can deactivate the output channel. It is to beappreciated that such computations can alternatively be performed by thesystem control 202 (e.g., depending on the processing ability affordedthe waveform controllers).

Still another example might be to perform charge balancing in theoperation of the amplifiers 210 based on feedback 216 received from therespective output channels 208. The monitoring of the charge at a givenchannel 208, for instance, can help ensure that no net DC voltageappears in any of the channels 208. The DC voltage for a given channel208 can be mitigated, at least in part, by employing the DC blockingcapacitors 211.

Those skilled in the art will understand and appreciate various types ofamplifiers 210 that can be utilized to amplify the input waveforms (fromthe waveform controllers 204) for driving the output channels 208. Thetype of amplifier will typically be selected to provide for low powerconsumption since the IPG 200 is intended to be implanted in a subject.As one example, the amplifiers 210 can be implemented as class Gamplifiers, which by adjusting the power supply voltage (or voltagerails) during operation, reduced power consumption can be achievedrelative to other amplifier types. As another example, the amplifiers210 can be implemented as class H amplifiers, which operate similar toclass G amplifiers as well as modulate the output based on the inputsignal. Other types of amplifiers can also be utilized, such asamplifiers designed to amplify audio signals and also operate with lowpower consumption (e.g., class D or switching power amplifier).

As mentioned above, the system control system 202 can communicate withthe waveform controllers 204, such as over a data bus 220. The bus 220can be bi-directional to allow communication of information between thesystem control 202 and one or more of the waveform controllers 204. Asone example, the bus 220 can be implemented as a serial peripheralinterface (SPI) bus that communicates SPI data 222, such as including aclock signal, a “data in” signal, and a “data out” signal. The bus 220can also include a “chip select” signal 224 to enable communication ofthe SPI data (data and clock signals) between the system control 202 anda selected one of the waveform controllers 204. Those skilled in the artwill appreciate that system 200 may also implement other bus topologies,such as I²C bus, system management bus (SMBus), as well as other knownor yet to be developed bus structures (e.g., including other serial andparallel bus structures).

As described herein, the system control 202 can employ the bus 220 toprogram each of the waveform controllers 204 as well as to receiveinformation from the waveform controllers. According to one aspect, thesystem control 202 can program some or all of the waveform controllers204 by storing one or more waveforms in the memory 206 for subsequentplay back. The system control 202 can also program the waveformcontroller 204 to control which of the stored waveforms are to be playedback during operation. The system control 202 can also program operationof the output system 212 of each of the waveform controllers 204 tocontrol to which amplifier 210 the analog output waveforms are to beprovided.

As another example, the system control 202 can program the waveformcontrollers 204 to adjust or scale parameters of the waveform(s) thatare being played back. For example, the parameters can includeamplitude, pulse width, and pulse duration. The system control 202 canalso program the waveform controllers 204 to control the number of pulsetrains of the one or more stored waveforms that are supplied as thecorresponding analog output waveform. As described herein, the waveformsthat are stored in the memory 206 of the respective waveform controllers204 can be pre-recorded waveforms (recorded from an animal or from awaveform generator) or the waveforms can be synthesized waveforms thatare provided to the system 200 as they are generated remotely.

The waveform controllers 204 can also provide information to the systemcontrol 202 via the bus 220. The waveform controllers 204 can provideinformation to the system control 202 in response to an interrogationcommand from the system control or automatically in response todetecting one or more predetermined conditions. For example, one or moreof the waveform controllers 204 can provide impedance information to thesystem control based on the feedback 216 received from one or moreamplifiers (e.g., raw feedback data and/or preprocessed informationindicating detected impedance is outside of expected operatingparameters). Other diagnostic information associated with operation ofthe waveform controllers 204 or as may be sensed by one or more sensors(not shown) can also be sent from the waveform controllers to the systemcontrol 202. This information may be stored in the memory 228 and actedon by one or more processes running in the system control 202.Alternatively, some or all such information can be sent to a remotestation (e.g., an external programmer) via a communication system 232.

The system control 202 includes a system processor 226 and associatedmemory 228. For example, the system processor 226 can be implemented asa microcontroller unit that includes the memory 228. Alternatively oradditionally, the memory 228 can be implemented separately from theysystem processor 226.

The memory 228 can include instructions and data to control the overalloperation of the system 200. For instance, the memory 228 can storeinstructions and information to enable communication with the waveformcontrollers 204 over the bus 220. The memory 228 can also storeinstructions that define which of the amplifiers 210 are to be activatedas well instructions that define operating parameters of the respectiveamplifiers (collectively referred to as “amplifier controlinstructions”). The system control 202 thus can employ the amplifiercontrol instructions to provide corresponding control signals, indicatedat 230, to control each of the amplifiers 210. The control signals 230,for example, can activate a given amplifier 210 as well as place adeactivated amplifier into a sleep mode (e.g., for power conservation).The control signals 230 can also adjust one or more amplifier operatingparameters, such as to adjust amplifier gain or to adjust voltage railsfor a respective amplifier. The memory 228 can also store schedulinginformation can identify which waveform or combination of waveforms areto be played back by each of the waveform controllers 204 as well asparameters of the respective waveforms that are to be played back.

The memory 228 can also store waveform data representing the waveformsthat are being programmed into the waveform controllers. The waveformscan be stored in the memory 228 temporarily (e.g., during programming)or copies of all waveforms can be stored in the memory until erased oroverwritten. The copies of waveforms stored in the memory 228 canprovide a set of stored waveforms (internal to the IPG) that can beemployed for programming the waveform controllers 204. For example, ifadjustments need to be made to one or more waveforms (e.g., duringoperation), the adjustments may be made by the system control 202selecting one or more alternative waveforms from the memory 228 andprogramming corresponding waveform controllers 204. Adjustments can alsobe implemented by appropriate scaling of waveform parameters.Alternatively, the one or more alternative waveforms can be providedfrom a remote external programmer, such as described herein.

The communication system 232 is coupled with an antenna 234 forcommunicating information wirelessly relative to the IPG. As mentionedherein, the information can include program instructions effective tocontrol operation of the IPG system 200, including the system control202, the waveform controllers 204 and the amplifiers 210. The systemcontrol 202 can receive such program instructions and store them in thememory 228, some of which can be transferred to program respectivewaveform controllers 204 via the bus 220.

The communication system 232 can be implemented as including a receiverand a transmitter (a transceiver) that provide for bi-directionalcommunication of information relative to the IPG 200. A remote stationthus can communicate with the IPG by employing a predetermined wirelessprotocol. The communication system 232 can implement any one of aplurality of known wireless communication protocols, such as Bluetooth,Digital Enhanced Cordless Telecommunications (DECT), OBject Exchange(OBEX) communication protocol, as well as other known and yet to bedeveloped protocols.

The communication system 232 can also employ security features toinhibit unintentional or unauthorized access to the IPG 200. Thesecurity features can be part of the communication protocol beingimplemented by the communication system 232 or the features can bespecific to the IPG system 200. For the example of implementingBluetooth wireless communications, the communication system 232 canimplement the SAFER+ algorithm for authentication and key generation.Alternatively, the use of a predefined key or ID associated with the IPG200 may be required as part of data transmission to identify acommunication as being an authorized communication.

The IPG 200 also includes a battery 236 that stores energy for providingpower to the IPG. The battery 236 can include one or more cellsconfigured to store a charge for providing corresponding DC voltage. Thebattery 236 can be replaceable and/or rechargeable depending on theexpected duration that the IPG 200 will be implanted in a patient. Thebattery 236 can be directly coupled to the system control 202 andprovide an output voltage to a power converter 238. The power converter238 can provide a suitable regulated output voltage to the systemcontrol 202 and to the amplifiers 210 and the waveform controllers 204.The particular voltage provided by the converter 238 can vary based onthe operating requirements of the circuitry implemented in the IPGsystem 200. Additionally, the amplifiers (e.g., if implemented as classG or H amplifier) 210 can implement load tracking functions, such as toadjust voltage rails as a function of the load requirements of theanalog output waveforms being provided to the output channels 208.

FIGS. 4A and 4B depict examples of different basic configurations thatcan be utilized to implement the waveform controllers 204 of FIG. 4. InFIG. 4A, the waveform controller includes a processor 250 and associatedmemory 252. The memory 252 can be internal to the processor 250,external to the processor as shown, or a portion of the memory can beinternal and another part can be external relative to the processor. Theprocessor 250 is also coupled to supply an output waveform signal 253 toa multiplexer 254. The processor 250 supplies the output waveform signal253 based on one or more waveforms retrieved from the memory 252. Themultiplexer 254 distributes the output waveform signal to one or moreselected outputs 256 for play back over a selected set of one or moreoutput channels. For instance, the processor 250 can provide a selectionsignal (SEL) to the multiplexer 254 to control which channel amplifiersreceive the output waveform via the outputs 256. It will be appreciatedthat that the waveform controller also includes digital-to-analogconverter (not shown) to convert the stored digital waveform data into acorresponding analog output waveform that is provided to the selectedoutputs 256.

The waveforms can be stored in the memory 252 in response to waveformdata provided to the waveform controller, such as from the systemcontrol 202 (FIG. 4). Control instructions can also be stored in thememory 252 to provide for other closed loop control of the waveformcontroller and the amplifiers being driven with the analog outputwaveforms. For instance, the processor 250 can also receive one or moresignals, indicated at 258, from the amplifiers 210 or from sensors (notshown). The processor 250 can utilize the one or more signals 258 toadjust one or more parameters of the output waveform, to select one ormore alternative waveforms, or to adjust operation of the amplifiers210. By employing the processor 250 and memory 252 in the waveformcontroller, those skilled in the art will understand and appreciatevarious types of intelligent control that can be implemented at thewaveform controller (e.g., including real time and/or periodicadjustments).

FIG. 4B depicts an example of another waveform controller 204 thatincludes a direct memory access (DMA) controller 260 that is connectedwith associated memory 262. The DMA controller 260 is programmed and/orconfigured to transfer one or more predetermined blocks of data from thememory 262 to an output multiplexer 264. As described herein, the blocksof data correspond to one or more waveforms that are stored in thememory 262. The system control 202 (FIG. 4), for example, can provide anINPUT signal to cause the DMA controller 260 to write the waveform datato the memory 262 (e.g., during a programming mode). The system control202 can also program the DMA controller 260 to retrieve and transfer thestored waveform data to the multiplexer 264 (e.g., during normaloperation). The system control 202 can also program the multiplexer 264to distribute the corresponding analog output waveform to one or moreamplifiers 210. For example, a corresponding selection signal (SEL) canbe provided to configure the multiplexer 264 to distribute the outputwaveform to a selected set of one or more amplifiers 210. The SEL signalcan be stored in the waveform controller, such as based on instructionsfrom the system control 202 (FIG. 4).

It will be appreciated that variations of the basic approaches of FIGS.4A and 4B may also be implemented. For instance, a processor and a DMAcontroller may be implemented in the waveform controller 204 so thatplay back of stored waveform(s) can be implemented by the DMA controllerand other intelligent controls are executed by the processor. Thiscombined approach can help reduce the processing requirements of theprocessor, although generally at the expense of additional circuitry toimplement the DMA controller. The cooperation of the processor and theDMA controller may also be balanced according to the power requirementsof the IPG 200. Additionally, those skilled in the art will appreciateother aspects and features that may be implemented in the waveformcontrollers of FIGS. 4A and 4B (e.g., including buses, connections andpower inputs and filters).

FIG. 5 depicts an example of an IPG 300 that may be implementedaccording to an aspect of the present invention. The IPG 300 includes asubstantially biocompatible housing 302 that encapsulates IPG circuitry303 that is programmed (or programmable) and configured to implement thefunctions described herein. The IPG circuitry 303 can correspond to anyof the types of systems shown and described herein (e.g., FIGS. 1-4) aswell as combinations thereof consistent with the teachings contained inthis document. The housing 302 can be hermetically sealed. The circuitry303 can include a control system 304 that can include a play back system306 and memory 308, such as described herein. The control system 304 canprovide one or more analog output waveforms (from the memory) to anassociated output system 310. The output system 310 distributes one ormore output waveforms to channels 312 associated with each of aplurality of respective output ports. As described herein, the waveformsprovided to each channel 312 can be the same or different.

In the example of FIG. 5, a pair of output receptacles 314 and 316 eachprovides electrical access to the plurality of output channels 312. Forinstance, each channel can include an electrical contact that can beelectrically connected to a corresponding mating part of a lead system(not shown). One type of lead system includes male connector parts thatare dimensioned and configured for mating insertion into and withincorresponding female receptacles 314 and 316 (e.g., the leads areplugged into the receptacles). The playback system 306 thus can delivera corresponding amplified electrical stimulus to one or more electrodes(through the lead system) according to the output waveform delivered toeach of the respective output channels 312. The number of leads andnumber channels for each receptacle can vary according to patient andpathology requirements.

The IPG 300 also includes a communication system 320 that is configuredto enable communication with an external programmer (see, e.g., FIG. 2).For instance, the communication system 320 can employ wirelesscommunication according to a predetermined communication mode via one ormore antenna 322. The control system 304 can communicate with theexternal programmer via the control system. The communication may bebi-directional. For example, the control system 304 can receive programinstructions and waveform data that can be stored in the memory, such asdescribed herein. Additionally, the control system 302 can senddiagnostic information and report on operating parameters of the IPGsystem 300 and of lead system that may coupled to the IPG system, suchas described herein.

What have been described above are examples of the present invention. Itis, of course, not possible to describe every conceivable combination ofcomponents or methodologies for purposes of describing the presentinvention, but one of ordinary skill in the art will recognize that manyfurther combinations and permutations of the present invention arepossible. Accordingly, the present invention is intended to embrace allsuch alterations, modifications, and variations that fall within thespirit and scope of the appended claims.

1. A method for neuromodulation to treat a movement disorder,comprising: recording an input waveform from a first site in the nervoussystem in a source subject while the source subject is performing atask, wherein the first site is selected from the group consisting of:motor cortex, premotor cortex, thalamus, red nucleus, olivary nucleus,and dentate nucleus; and applying an output waveform to a second site inthe nervous system in a target subject suffering from the movementdisorder while the target subject is performing the same task, whereinthe second site is selected from the group consisting of: motor cortex,premotor cortex, thalamus, red nucleus, olivary nucleus, and dentatenucleus; wherein the output waveform is identical to the input waveformor derived from the input waveform.
 2. The method of claim 1, whereinthe source subject and target subject are different subjects.
 3. Themethod of claim 2, wherein the source subject is a non-human primate. 4.The method of claim 2, wherein the second site in the nervous systemanatomically corresponds to a structure that is neurologically distal tothe first site in the nervous system.
 5. The method of claim 1, whereinthe source subject and target subject are the same subject.
 6. Themethod of claim 5, wherein the second site is the corresponding anatomicstructure that is contralateral to the first site.
 7. The method ofclaim 6, wherein the first site is healthy or at least partiallyfunctioning, and wherein the second site is diseased.
 8. The method ofclaim 5, wherein the second brain site is neurologically distal from thefirst brain site.
 9. The method of claim 1, further comprisingpositioning an electrode at the second site, and applying the outputwaveform through the electrode.
 10. The method of claim 1, furthercomprising modifying the input waveform to generate the output waveform.11. The method of claim 1, further comprising sensing a body activity.12. The method of claim 11, further comprising, in response to the bodyactivity sensed, modifying the output waveform.
 13. The method of claim12, wherein the body activity being sensed is limb motion.
 14. Themethod of claim 1, wherein the task is a forelimb or hindlimb motortask.
 15. The method of claim 1, further comprising: combining aplurality of different input waveforms to form a composite outputwaveform.
 16. A method for neuromodulation to treat a movement disorder,comprising: recording an input waveform from a first site in the nervoussystem in a source subject, wherein the first site is selected from thegroup consisting of: motor cortex, premotor cortex, thalamus, rednucleus, olivary nucleus, and dentate nucleus; and applying an outputwaveform to a second site in the nervous system in a target subjectsuffering from the movement disorder, wherein the second site isselected from the group consisting of: motor cortex, premotor cortex,thalamus, red nucleus, olivary nucleus, and dentate nucleus; wherein theoutput waveform is identical to the input waveform or derived from theinput waveform wherein the second site in the nervous systemanatomically corresponds to the first site in the nervous system.